An index is compiled from securities selected according to specified rules and shows their combined performance as a single number. The index value itself is meaningless—what matters is its change relative to previous periods.
The weighting method determines what is being measured. Most commonly, capitalization weighting is used: the larger the company, the greater its influence on the index. Sometimes only the freely circulating portion of shares is considered, since securities held by the state or major shareholders do not actually participate in trading.
Indices are used as benchmarks for evaluating portfolio performance and as the basis for index funds that replicate their composition.
This limitation is significant for the Uzbek market: an index is informative only when the securities included in it have sufficient liquidity. If transactions for some issuers occur rarely, prices in the calculation remain outdated, and a single atypical transaction can sharply shift the entire value. Therefore, assessing portfolio performance here is better done not by a single index, but by several benchmarks simultaneously.